?– 302 Moved Temporarily This response also provides a new address, but the
address is a temporary address; therefore, receiving devices will not use this information
to update address books.
?– 305 Use Proxy Indicates the address of a proxy that must be used to provide a
requested service.
?– 380 Alternative Service Indicates that the call was not successful but other
services requested in the same session request can be provided.
The exact response provides the reason for the redirect. For example, the subscriber
may have temporarily moved to another network or may have changed networks permanently.
The URI that the session is being redirected to is provided as well.
4xx Client Failure Responses When a device receives a request that it cannot accept
because of an error made by the originator, then it will respond using the client failure
responses. For example, a request sent to a device can be denied prior to a dialog being
established by returning the 403 Forbidden response. Here are the defined client error
messages:
Session Initiation Protocol (SIP) 67
?– 401 Unauthorized This is sent by the S-CSCF to challenge a device when it first
sends a REGISTER. The device will then send another REGISTER containing
credentials per the registration process.
?– 403 Forbidden This is used when a call is being rejected prior to a dialog being
established.
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